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My experimental system


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Hi All, 

Neil from Pretoria here. My first post, so I thought a picture of my weekend hobby would suffice. :-)


Starting from humble beginnings: a single 20W panel, 6A Stecca PWM controller and 7.2Ah battery, it has evolved quite a bit. I'm lucky in that all the kit is leftovers from other projects, so it grows as time goes on.



- 1200Wp solar array, Soon to double in size.

- 200Ah (@24V) battery bank (4x Lead Crystal @100Ah)

- 45A Tristar MPPT controller, and old 1500W inverter.

- most importantly a BMV702. My insight into the system operation grew by leaps and bounds after this little piece of crucial kit. For anybody without this - great investment. The little flashy-flashy led on the charge controller simply doesn't say anything useful.


I know it looks like a mess, but it's actually quite neat underneath. It's just because the layout keeps on changing, and the bunch of cables hanging in loops was the DVR and video system that hasn't been fully "neatened up". The system is also highly over designed ITO cable diameters.... seeing that I know it will expand in time.


The second shelf from the bottom is a MPPT charge controller feeding from the 24V system to power a 12V battery. It's not always on, so I don't drain the main system at night. It works great - just don't try to do this with a PWM charge controller. Yes, a DC-DC converter would have been better, but hey, I had the stuff and wanted to see if it works.


So as things go, for a guy that sells vandal and theft proof solar panels for a living: My solar panels are bound to the little structure with wire. eish. But, my new high security solar panel clamp is almost finalised at the patent attorney, and the array will get a revamp. 
Currently busy experimenting with improving freezer effectivity. Busy wiring thermocouples into a new freezer I got for the experiment.
Biggest problem with the system: I committed the ultimate sin, and expanded a couple month old 2x100Ah battery bank by later adding additional 2x100Ah batteries. I'm currently measuring quite a voltage drop on the old battery string. Makes for lots of alarms from the BMV.



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I also started with 20w panel, ended up with 3 x 310w and 1 x 200w (melted the other one's connection box).
Also have spare parts (some smokeless) and never seem to get the wiring neat and tidy, always something changing. :-) 


Is the cabinet always open? Do you not get a heat issue if it is closed? I also have a Tristar and sometimes it works hard, generating a bit of heat.

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:-) @Triplett: just the battery bank gets closed up, incase my little one fiddles around. The shelves stay open, and yes, the Tristar can heat up. I've seen about 50degC on it.

On one of the theft resistant enclosures that I've designed a lot of attention was paid to heat management. Luckily I've never seen hot batteries!

@Slingers: the mppt used is also a morningstar. The manual reads: the charge controller will limit the input power to the rated maximum... Just check that the one intended for this task does the same! I want to add a relay and a timer for an "artificial sun"... Is a solidstate relay the right choise?

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